path_to_handle, path_to_fshandle, fd_to_handle, handle_to_fshandle,
open_by_handle, readlink_by_handle, attr_multi_by_handle,
attr_list_by_handle, fssetdm_by_handle, free_handle, getparents_by_han‐
dle, getparentpaths_by_handle - file handle operations
int path_to_handle(char *path, void **hanp, size_t *hlen);
int path_to_fshandle(char *path, void **hanp, size_t *hlen);
int fd_to_handle(int fd, void **hanp, size_t *hlen);
int handle_to_fshandle(void *hanp, size_t hlen, void **fshanp, size_t
int open_by_handle(void *hanp, size_t hlen, int oflag);
int readlink_by_handle(void *hanp, size_t hlen, void *buf, size_t bs);
int attr_multi_by_handle(void *hanp, size_t hlen, void *buf, int
rtrvcnt, int flags);
int attr_list_by_handle(void *hanp, size_t hlen, char *buf, size_t buf‐
siz, int flags, struct attrlist_cursor *cursor);
int fssetdm_by_handle(void *hanp, size_t hlen, struct fsdmidata
void free_handle(void *hanp, size_t hlen);
int getparents_by_handle(void *hanp, size_t hlen, parent_t *buf, size_t
bufsiz, parent_cursor_t *cursor, unsigned int *count, unsigned
int getparentpaths_by_handle(void *hanp, size_t hlen, parent_t *buf,
size_t bufsiz, parent_cursor_t *cursor, unsigned int *count,
unsigned int *more);
These functions provide a way to perform certain filesystem operations
without using a file descriptor to access filesystem objects. They are
intended for use by a limited set of system utilities such as backup
programs. They are supported only by the XFS filesystem. Link with the
libhandle library to access these functions.
A handle, hanp, uniquely identifies a filesystem object or an entire
filesystem. There is one and only one handle per filesystem or
filesystem object. Handles consist of some number of bytes. The size
of a handle (i.e. the number of bytes comprising it) varies by the type
of handle and may vary for different objects of the same type. The
content of a handle is opaque to applications. Since handle sizes vary
and their contents are opaque, handles are described by two quantities,
a pointer (hanp) and a size (hlen). The size, hlen, indicates the num‐
ber of bytes in the handle which are pointed to by the pointer.
The path_to_handle() function returns the handle for the object given
by the path argument. If the final component of the path name is a sym‐
bolic link, the handle returned is that of the link itself.
The path_to_fshandle() function returns the handle for the filesystem
in which the object given by the path argument resides.
The fd_to_handle() function returns the handle for the object refer‐
enced by the fd argument, which must be a valid file descriptor.
The handle_to_fshandle() function returns the handle for the filesystem
in which the object referenced by the handle given by the hanp and hlen
The open_by_handle() function opens a file descriptor for the object
referenced by a handle. It is analogous and identical to open(2) with
the exception of accepting handles instead of path names.
The readlink_by_handle() function returns the contents of a symbolic
link referenced by a handle.
The attr_multi_by_handle() function manipulates multiple user
attributes on a filesystem object. It is analogous and identical to
attr_multif(3) except that a handle is specified instead of a file
The attr_list_by_handle() function returns the names of the user
attributes of a filesystem object. It is analogous and identical to
attr_listf(3) except that a handle is specified instead of a file
The fssetdm_by_handle() function sets the di_dmevmask and di_dmstate
fields in an XFS on-disk inode. It is analogous to the XFS_IOC_FSSETDM
xfsctl(3) command, except that a handle is specified instead of a file.
The free_handle() function frees the storage allocated for handles
returned by the following functions: path_to_handle(), path_to_fshan‐
dle(), fd_to_handle(), and handle_to_fshandle().
The getparents_by_handle() function returns an array of parent_t struc‐
tures for each hardlink to the inode represented by the given handle.
The parent structure encodes the parent inode number, generation number
and the basename of the link. This function is not operational on
The getparentpaths_by_handle() function is identical to the getpar‐
ents_by_handle() function except that instead of returning the basename
it returns the path of the link up to the mount point. This function
is also not operational on Linux.
The function free_handle() has no failure indication. The other func‐
tions return the value 0 to the calling process if they succeed; other‐
wise, they return the value -1 and set errno to indicate the error.
EACCES Search permission was denied for a component of path.
EBADF fd is not a valid and open file descriptor.
EFAULT An argument pointed to an invalid address.
EINVAL path is in a filesystem that does not support these functions.
ELOOP Too many symbolic links were encountered in translating the path
A component of path or the entire length of path exceeds
ENOENT A component of path does not exist.
EPERM The caller does not have sufficient privileges.
SEE ALSOopen(2), readlink(2), attr_multi(3), attr_list(3), xfsctl(3), xfs(5).